Ir L3 edge Resonant Inelastic X-ray Scattering (RIXS) and La2 Resonant X-ray Emission Spectroscopy (RXES) have been used to investigate A2IrO3 (A= Na or Li) and CuIr2S4. First principle calculations show that the low-energy dd-excitations in the RIXS spectra of A2IrO3 originate from a split jeff=3/2 to jeff=1/2 excitation. A magnetic excitation is observed in Na2IrO3, whose dispersion is consistent with the theoretical prediction including a bond-dependent Kitaev interaction between jeff=1/2 magnetic moments. In CuIr2S4, RXES measurements reveal that the unoccupied Ir t2g level shift upward in energy as a result of the metal-insulator transition, confirming density functional theory calculations. In the x-ray irradiation induced phase of CuIr2S4, a mid-infrared peak emerges in the RIXS spectrum around 0.4 eV, suggesting that both the crystal structure and the electronic structure are modified due to x-ray irradiation.
The size of the magnetic moments in Fe based superconductors has been investigated using Fe Kb X-ray Emission Spectroscopy (XES). Local magnetic moments are found in Fe pnictides and chalcogenides, independent of temperature or carrier concentration. This result supports the notion of local moments coexisting with metallic bands. Our investigation of Ca{1-x}RExFe2As2 (RE=La, Pr, and Nd) shows results consistent with a spin-state transition. We argue that the gradual change of the spin-state over a wide temperature range reveals the importance of multiorbital physics, and in particular the competition between the crystal field split Fe 3d orbitals and the Hund's rule coupling.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/43567 |
| Date | 09 January 2014 |
| Creators | Gretarsson, Hlynur |
| Contributors | Kim, Young-June |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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